The paper analyses the impact of Electric Vehicle(EV) integration into different power systems and their flexibility potential in mitigating the uncertainty and variability of renewable Energy sources (RES) generation. The problem is cast as Mixed Integer Linear Programming (MILP) unit ommitment, modelling different generation mix/technologies over a number of scenarios. The results, as expected, show that different EV charging strategies have different impacts on power system operation and unit scheduling. In addition, the analyses support the premises that the greater number of EVs, with coordinated charging strategies, can have environmental enefits in terms of reducing CO2 emissions in addition to reducing wind curtailment and system operation costs. These benefits are more obvious in low flexible power systems characterized by dominantly thermal power plants, while they are less pronounced in balanced hydro thermal systems.